Briefing of Crane machine

A crane is a machine,usually equipped with hoisting ropes,wire ropes or chains and pulleys,that can be used to raise and lower materials as well as move them horizontally.It is mainly used for lifting heavy objects and transporting them to other places.The device uses one or more simple machines to create a mechanical advantage that moves loads beyond a human's normal ability.Cranes are commonly used to load and unload goods in transportation,transport materials in construction,and assemble heavy equipment in manufacturing.The first known crane was the shaduf,a water-lifting device that was invented in ancient Mesopotamia (modern-day Iraq) and then appeared in ancient Egyptian technology.Construction cranes later appeared in ancient Greece and were powered by humans or animals (such as donkeys) and used to construct buildings.Larger cranes were later developed in the Roman Empire,using human treaded wheels,which could lift heavier weights.During the High Middle Ages,harbor cranes were introduced to load and unload ships and assist in construction-some built in stone towers for added strength and stability.The earliest cranes were built of wood,but with the advent of the Industrial Revolution, cast iron, steel and steel took over.For many centuries electricity was provided by the physical exercise of man or animals,although the cranes in watermills and windmills could be driven by harnessed natural power.The earliest mechanical power was provided by steam engines,the first steam cranes were introduced in the 18th or 19th century,and many remained in use until the late 20th century.Modern cranes generally use internal combustion engines or electric motors and hydraulic systems to provide greater lifting capacity than before,albeit manually ut-sized cranes where providing power is economical.There are many different types of cranes,each suitable for a specific purpose.Sizes range from the smallest jib cranes,used in workshops,to the tallest tower cranes,used in the construction of high-rise buildings.Micro cranes are also used in the construction of tall buildings,facilitating construction by reaching tight spaces.Large floating cranes are generally used to build oil rigs and salt wrecks.Some lifting machinery does not strictly meet the above definition of cranes,but is generally referred to as cranes, such as stackers and truck-mounted cranes. 

Machinery and Operation

In contrast to modern cranes,medieval cranes and cranes-much like their Greek and Roman counterparts were primarily used for vertical lifting and not for moving loads horizontally over considerable distances.As a result, lifting work was organized differently in the workplace than it is today.For example,in building construction,suppose a crane lifts stones into place directly from the bottom,or from a position opposite the center of the wall to where two teams work at each end of the wall.In addition, the crane supervisor, who usually gives orders to castor workers from outside the crane, is able to steer the movement laterally via small ropes attached to the load.The slewing crane, which allows the load to rotate and is therefore particularly suitable for dock work, appeared as early as 1340.While ashlar blocks were lifted directly by slings,lewis,or devil clamps (Teufelskralle, Germany),other objects were previously placed in containers such as pallets, baskets, wooden boxes, or barrels.It is worth noting that medieval cranes were rarely equipped with ratchets or brakes to prevent the load from running backwards.This strange absence can be explained by the fact that the high friction exerted by medieval tread wheels usually prevented the wheels from accelerating out of control.

Port use

According to the unknown "state of knowledge" of antiquity,stationary harbor cranes are considered a new development in the Middle Ages. A typical harbor crane is a pivoting structure with twin tread wheels.These cranes are placed quayside for loading and unloading, where they replace or supplement older lifting methods such as see-saws, winches and yards.Two different types of harbor cranes can be identified,which have a different geographical distribution: gantry cranes rotating on a central vertical axis are common on the Flemish and Dutch coasts,while tower cranes are often seen in German seaports and inland ports.Feature,where the winches and treadwheels are in a solid tower where only the cantilever and roof rotate.Quayside cranes were not adopted in the Mediterranean and highly developed Italian ports after the Middle Ages,where authorities continued to rely on the labor-intensive method of unloading goods on ramps.Unlike construction cranes, where work speed is dictated by the relatively slow progress of masons, harbor cranes often employ twin tread wheels for faster loading.Two treadwheels,estimated to be 4 m in diameter or greater,are attached to each side of the shaft and rotate together.They have a capacity of 2-3 tons,apparently corresponding to the customary dimensions for sea freight.Today,according to one survey,15 pre-industrial caster harbor cranes still exist throughout Europe.Some harbor cranes were used exclusively for fitting masts to newly built sailing ships, for example in Gdańsk,Cologne and Bremen.In addition to these fixed cranes,the use of floating cranes that can be flexibly deployed throughout the port area began in the 14th century.

Early modern

Renaissance architect Domenico Fontana used an elevator tower similar to that of the ancient Romans to relocate Rome's 361-ton Vatican obelisk in 1586.It is evident from his report that coordinating lifts between different pulling teams required considerable attention and discipline, as excessive stress on the ropes could cause them to break if force was applied unevenly.Cranes were also used domestically during this period.Chimney or fireplace hoist for swinging pots and kettles over the fire,height adjusted by boom.